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Covariance Variables may change in relation to each other Variables may change in relation to each other measures how much the movement in one variable predicts the movement in a corresponding variable Covariance measures how much the movement in one variable predicts the movement in a corresponding variable 3R F Riesenfeld Sp 2010CS5961 Comp Stat

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Covariance Variables that inversely, like smoking and lung capacity, tend to appear on opposite sides of the group means Variables that covary inversely, like smoking and lung capacity, tend to appear on opposite sides of the group means When smoking is above its group mean, lung capacity tends to be below its group mean. When smoking is above its group mean, lung capacity tends to be below its group mean. Average measures extent to which variables covary, the degree of linkage between them Average product of deviation measures extent to which variables covary, the degree of linkage between them 8R F Riesenfeld Sp 2010CS5961 Comp Stat

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The Sample Covariance Similar to variance, for theoretical reasons, average is typically computed using ( N -1 ), not N. Thus, Similar to variance, for theoretical reasons, average is typically computed using ( N -1 ), not N. Thus, 9R F Riesenfeld Sp 2010CS5961 Comp Stat